**3.5. Environmental transport of contaminants**

96 New Approaches to the Study of Marine Mammals

NR= non reported a Borga *et al*. [15].

feeding relationships.

C*PREDATOR*>C*PREY*, BMF > 1).

Galápagos Islands (Ecuador) Galapagos sea lion

 BMFTL BMFTL *p*,*p*'-DDE 139−2014 319 *p*,*p*'-DDT 142−760 NR ∑DDT 122−1631 NR *β*-HCH 63.0−552 4.1 *cis*-chlordane 32.7−587 NR *trans*-chlordane 7.34−128 NR *trans*-nonachlor 73.7−1609 141.7 ∑Chlordanes 54.1−1029 NR PCB 52 11.0−11.6 NR PCB 99 15.5−33.1 147.0 PCB 101 9.53−17.7 NR PCB 105 7.51−20.0 18.1 PCB 118 11.2−28.8 41.6 PCB 138 13.9−53.9 327.7 PCB 153 17.7−72.2 416 PCB 180 7.72−66.9 NR ∑PCBs 11.2−37.2 NR Ratio BMFTL*p*,*p*'-DDE to BMFTL PCB 153 7.85−27.9 0.77

**Table 3.** Comparison of BMFTL for remote marine food chains between the Galapagos Islands and an Arctic reion for selected organochlorine pesticides and PCBs. The BMFTL for Galapagos sea lions are expressed as the range of concentration ratios of both sea lion/thread herring and sea lion/mullet

It is well recognized that the increase in organic chemical concentrations in lipids of organisms with increasing trophic level in food-webs originates from the magnification of the chemical concentration in the gastro-intestinal tract caused by food digestion and absorption [5,14]. In this study, the biomagnification capacity of organochlorine contaminants in the tropical food chain of the Galapagos sea lion is established (i.e.

However, a range of various factors directly or indirectly affect magnification process in predators, including animal ecologies and physiologies, feeding preferences, life history parameters (sex, age, body size and corporal condition), reproduction, geographic locations and stochastic-climatic events. Furthermore, the composition of contaminants can be shaped through toxicokinetics processes (i.e., uptake, metabolism, respiration and excretion), influencing the persistence and food-web biomagnification of POPs. Due to these factors, it is complex to elucidate whether a wild predator is at a steady state with its diet; therefore,

**3.4. Biomagnification behaviour of POPs in the Galapagos food-chain** 

Barents Sea Harp seala

> Lack of significant differences and consistent uniformity of PCBs and OC pesticides, particularly for PCBs, among sites might indicate common sources of contamination. Concentrations of PCBs were also similar among rookeries in an earlier baseline study [34], although DDT concentrations were found to be significantly different [35]. Furthermore, principal components analysis represented a more comprehensive approach for exploring spatial differences and behaviour of POPs. The two first principal components (i.e., PC 1 and PC2) accounted for 55.2% of the total variation in Galapagos sea lion pups. PCA score plot results for the 2008 data further revealed that contaminants follow a similar trend, aggregated near to the centre of the axes, among sites, showing lack of discrimination and differentiation in contaminant patterns (Figure 6a). The first principal component (i.e.,

loading plots, PC1: 40.1% of the total variance) segregated in a significant degree the heavier PCB congeners (upper and lower left quadrants) from the lighter PCBs (upper and lower right quadrants; as seen in Figure 6b). A high positive PC1 score was correlated with higher percentages of low chlorinated PCBs (e.g., PCBs 43/49, 47/48/49, 52, 60, 61, 66, 74, 85, 86/97,87, 92, 95, 101, 110, 123, 132, 135, 136, 141, 144, 149) and *p*,*p*'-DDD, *p*,*p*'-DDT, dieldrin, *cis*-nonachlor, *trans*-chlordane, *cis*-chlordane and *β*-HCH, while a high negative score in PC 1 (upper and lower left quadrant) was correlated with a lower proportion of heavily and several, more persistent chlorinated PCBs (e. g. PCBs 118, 138/163/164, 137, 153, 158/160, 171, 177, 180, 183, 170/190, 172/192, 193, 194, 195, 196/203, 201, 202), as well as the semi-volatile and more bioaccumulative *p*,*p*'-DDE. These patterns show that PC1 appeared to be related to vapour pressure (Henry's Law constant or H) due to a high contribution of more volatile halogenated contaminants (pesticides) and less chlorinated (lighter) PCB congeners. A significant correlation was also observed between the log of the Henry's law constant (Log H) for the PCBs and PC1 (the variable loadings of the first principal component;*p* < 0.05, *r* = 0.27; Figure 7), suggesting that log H represented an important factor influencing the transport pathways and partitioning of PCB mixtures in remote environments; and, therefore, affecting the ultimate composition pattern observed in Galapagos sea lions. The Henry's law constant for each PCB is a fundamental parameter that represents the air-water equilibrium partitioning between surface waters and the atmosphere [57]. This indicates that local sources of exposure for high chlorinated PCBs are minimal in the Galapagos and that most of the contamination by POPs is coming from common atmospheric or continental sources.

Assessing Biomagnification and Trophic Transport of Persistent Organic Pollutants in the Food Chain of the Galapagos Sea Lion (*Zalophus wollebaeki*): Conservation and Management Implications 99

**136**

*p***,***p***'-DDT**

*p***,***p***'-DDD**

**86/97 110 47/48/75 135**

**61187**

**191 174 43/49**

**123** *cis***-nonachlor**

**60 <sup>144</sup> <sup>141</sup> <sup>92</sup>**

*cis-* **chlordane** *β* **-HCH**

**74**

*trans-c* **hlordane**

**dieldrin**

**85 179**

**132**

**146**

**156**

**200 185**

**197**

**-12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 t1 (40.1%)**

**99**

**mirex**

**155**

**154**

**167**

*trans-* **nonachlor**

**-1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 PC 1 (40.1%)**

**0**

**Figure 6.** Principal components analysis where the variance accounted for by each principal component

is shown in parentheses after the axis label: (a) score plots for patterns of POPs for the first two principal components shows that most of the pups from different rookeries have a similar contaminant pattern, as demonstrated here by the sample scores plot (t1 and t2) of 20 individuals; (b) loadings plots (PC1 and PC2) showing values of individual PCB congeners and pesticides in Galapagos sea lion pups,

**<sup>175</sup> <sup>130</sup>**

**178 <sup>142</sup> <sup>202</sup> 177**

**194 196/203**

*p***,***p***'-DDE**

**201**

**Isabela (Lobería Chica) Floreana (Lobería)**

**San Cristóbal (Puerto Baquerizo) San Cristóbal (Isla Lobos)**

**118**

where numbers are PCB congeners based on the IUPAC system.

**158/160 171 195 170/190**

**183 172/192 <sup>193</sup> <sup>105</sup> 180 128 138/163/164**

**153 137**

**-1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0**

**PC 2 (15.1%)**

**b**

**-12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12**

**t2 (15.1%)**

**a**

**0**

Dieldrin is a metabolite of aldrin, which was used for agriculture and public health purposes at beginning of the 1950s until its production was cancelled in 1989 in North America, but as with other pesticides, it continues to enter the environment via erosion of soils contaminated in the past and atmospheric deposition [58]. Mirex is a very unreactive and hydrophobic insecticide that was used in North America to control fire ants and as a fire retardant, persisting in the environment because of chronic small inputs from the atmosphere [59]. The presence of this compound in these blubber samples might be related to the past use of mirex in continental Ecuador [60] because of the possible use as insecticide (bait) to control invasive ants in the Galapagos and continental Ecuador. *β*-HCH is a major constituent of technical HCHs, which is likely one of the sources of this residue. Another potential source of *β*-HCH can be lindane (i.e., γ-HCH) since this pesticide is currently being used in several countries in the southern hemisphere as evidenced by its detection in blubber samples of southern elephant seals and minke whales (*Balaenoptera acutorostrata*) from the Antarctic Ocean [49, 61]. At the continental coast of Ecuador, lindane has recently been detected in sediments and aquatic organisms from the Taura River in the Gulf of Guayaquil [62]. The atmospheric influx of HCHs source formulations used in the Asian and South American tropics (i.e., lindane) and North America (i.e. technical HCH) might explain the incidence of *β*-HCH in these samples. Uncertain records of use of legacy OC pesticides exist for the Galapagos, although anecdotic suggested the use of CUP for agriculture (Dr. Alan Tye, former Head Scientist, Department of Plant and Invertebrate Science, Charles Darwin Foundation, Galapagos Islands), and the widespread use of DDT to eliminate introduced rats in the Galapagos by the US Armed Forces during the 1940s and 1950s [35].

loading plots, PC1: 40.1% of the total variance) segregated in a significant degree the heavier PCB congeners (upper and lower left quadrants) from the lighter PCBs (upper and lower right quadrants; as seen in Figure 6b). A high positive PC1 score was correlated with higher percentages of low chlorinated PCBs (e.g., PCBs 43/49, 47/48/49, 52, 60, 61, 66, 74, 85, 86/97,87, 92, 95, 101, 110, 123, 132, 135, 136, 141, 144, 149) and *p*,*p*'-DDD, *p*,*p*'-DDT, dieldrin, *cis*-nonachlor, *trans*-chlordane, *cis*-chlordane and *β*-HCH, while a high negative score in PC 1 (upper and lower left quadrant) was correlated with a lower proportion of heavily and several, more persistent chlorinated PCBs (e. g. PCBs 118, 138/163/164, 137, 153, 158/160, 171, 177, 180, 183, 170/190, 172/192, 193, 194, 195, 196/203, 201, 202), as well as the semi-volatile and more bioaccumulative *p*,*p*'-DDE. These patterns show that PC1 appeared to be related to vapour pressure (Henry's Law constant or H) due to a high contribution of more volatile halogenated contaminants (pesticides) and less chlorinated (lighter) PCB congeners. A significant correlation was also observed between the log of the Henry's law constant (Log H) for the PCBs and PC1 (the variable loadings of the first principal component;*p* < 0.05, *r* = 0.27; Figure 7), suggesting that log H represented an important factor influencing the transport pathways and partitioning of PCB mixtures in remote environments; and, therefore, affecting the ultimate composition pattern observed in Galapagos sea lions. The Henry's law constant for each PCB is a fundamental parameter that represents the air-water equilibrium partitioning between surface waters and the atmosphere [57]. This indicates that local sources of exposure for high chlorinated PCBs are minimal in the Galapagos and that most of the contamination by

Dieldrin is a metabolite of aldrin, which was used for agriculture and public health purposes at beginning of the 1950s until its production was cancelled in 1989 in North America, but as with other pesticides, it continues to enter the environment via erosion of soils contaminated in the past and atmospheric deposition [58]. Mirex is a very unreactive and hydrophobic insecticide that was used in North America to control fire ants and as a fire retardant, persisting in the environment because of chronic small inputs from the atmosphere [59]. The presence of this compound in these blubber samples might be related to the past use of mirex in continental Ecuador [60] because of the possible use as insecticide (bait) to control invasive ants in the Galapagos and continental Ecuador. *β*-HCH is a major constituent of technical HCHs, which is likely one of the sources of this residue. Another potential source of *β*-HCH can be lindane (i.e., γ-HCH) since this pesticide is currently being used in several countries in the southern hemisphere as evidenced by its detection in blubber samples of southern elephant seals and minke whales (*Balaenoptera acutorostrata*) from the Antarctic Ocean [49, 61]. At the continental coast of Ecuador, lindane has recently been detected in sediments and aquatic organisms from the Taura River in the Gulf of Guayaquil [62]. The atmospheric influx of HCHs source formulations used in the Asian and South American tropics (i.e., lindane) and North America (i.e. technical HCH) might explain the incidence of *β*-HCH in these samples. Uncertain records of use of legacy OC pesticides exist for the Galapagos, although anecdotic suggested the use of CUP for agriculture (Dr. Alan Tye, former Head Scientist, Department of Plant and Invertebrate Science, Charles Darwin Foundation, Galapagos Islands), and the widespread use of DDT to eliminate introduced rats in the Galapagos by the US Armed Forces during the 1940s and 1950s [35].

POPs is coming from common atmospheric or continental sources.

**Figure 6.** Principal components analysis where the variance accounted for by each principal component is shown in parentheses after the axis label: (a) score plots for patterns of POPs for the first two principal components shows that most of the pups from different rookeries have a similar contaminant pattern, as demonstrated here by the sample scores plot (t1 and t2) of 20 individuals; (b) loadings plots (PC1 and PC2) showing values of individual PCB congeners and pesticides in Galapagos sea lion pups, where numbers are PCB congeners based on the IUPAC system.

Assessing Biomagnification and Trophic Transport of Persistent Organic Pollutants in the Food Chain of the Galapagos Sea Lion (*Zalophus wollebaeki*): Conservation and Management Implications 101

higher than those in pups as DDTs accumulate throughout the animal's life because they are unable to offload contaminants during reproduction [35].While concentrations of DDTs pose protracted health risk because of lifetime exposure, the ∑PCB concentrations in Galapagos sea lion pups were lower than the new toxicity reference value of1,300 *μ*g/kg lipid for risk of immunotoxicity and endocrine disruption in harbor seals [67]. Other POPs with a similar mode of toxicity such as polybrominated diphenyl ether (PBDEs) flame retardants, which were also detected recently in these animals [34], can further exacerbate the immune and endocrine response. A compromised immune and endocrine system impairs the ability of

The Galapagos is one of the last evolutionary biology labs to preserve biodiversity. Yet, it has already been declared a UNESCO-Heritage site at risk because of invasive species, escalating human population growth and burgeoning tourism [68]. This study corroborated that POPs biomagnify to a significant degree in the tropical marine food chain of the Galapagos' marine ecosystem. This has important implications for management and control of organochlorine pesticides and conservation of marine ecosystems in tropical regions since pollution in the Galapagos has been categorized as an aesthetic issue rather than a chronic

Recently, the World Health Organization (WHO) has reactivated the use of the malaria mosquito-fighting pesticide DDT in tropical countries because of increasing malaria cases [69]. While the concentrations of DDT and associated health risks in wildlife are generally believed to be declining, this may no longer be the case in tropical countries where DDT is increasingly used and can biomagnify in food chains. A renewed use of DDT to combat malaria is likely to increase DDT concentrations in the Southern Hemisphere and in particular put bird and marine mammal populations at greater risk because of the

Since the ratification of the UN Stockholm Convention on POPs by Ecuador in 2004, the National Plan for the Inventory and Management of POPs was undertaken [70, 71]. DDT is included on Schedule 2 of the Stockholm Convention because of its damaging health effects in human and wildlife populations. Continuation of this initiative will help to control DDT contamination in the Galapagos. While DDT can save human lives, it can also adversely affect wildlife, local food production and opportunities for ecotourism. DDT use requires that tradeoffs need to be made between the conservation of valued, sensitive wildlife (e.g. Galapagos sea lions), fragile ecosystems and public health programs to control malaria.

Additional research and field sampling efforts may include other organisms integrating the trophic guilds of the Galapagos sea lion food web by measuring legacy and emerging POPs, stable isotopes and subsequent estimations of trophic levels. This will allow assessing in a higher degree the food web amplification of pollutants through the use of TMFs and food

web bioaccumulation models in marine ecosystem of the remote Galapagos Islands.

animals to combat disease and to successfully reproduce.

biomagnification of these substances in their food webs.

problem.

**4. Conservation implications and future research** 

**Figure 7.** Relationship between the Henry's law constant (Log H) for polychlorinated biphenyl (PCB) congeners and the first principal component (PC1). PC1 is significantly correlated with Log H for PCB congeners, suggesting that Galapagos sea lions from the remote Galapagos Islands are more exposed to light PCB mixtures, consistent with atmospheric signals. Numbers are PCB congeners based on the IUPAC system.

The long range atmospheric transport coupled with global fractionation have usually been described as the major mechanism delivering POPs from lower or mid latitudes to the polar regions [11, 63, 64], but it is likely that a similar mechanism or redistribution from mid latitudes may be also expanding or delivering volatile or semi-volatile pesticides such as HCHs and DDTs to isolated islands around the equator (i.e., the Galapagos Archipelago). These observations suggest that the contamination by organochlorine pesticides might be coming from both local and continental sources because pesticides were used in the recent past in countries in the southern hemisphere [49, 65]. Trans-Pacific air pollution of contaminants from tropical Asia to the eastern Pacific [63, 66] cannot be ruled out as a global and common pathway of POPs of atmospheric origin.

#### **3.6. Health risk assessment**

The health risk of POP biomagnification in Galapagos sea lions is of serious concern in the long term, as we have previously reported that 1% of the male pups exceeded the *p*,*p*'-DDE toxic effect concentration associated with potent anti-androgenic effects [35]. DDT concentrations in Galapagos sea lion pups are near levels expected to be associated with impacts on the immune systems, and in minor degree on the endocrine systems in males. Adult male Galapagos sea lions can be expected to exhibit DDT concentrations that are higher than those in pups as DDTs accumulate throughout the animal's life because they are unable to offload contaminants during reproduction [35].While concentrations of DDTs pose protracted health risk because of lifetime exposure, the ∑PCB concentrations in Galapagos sea lion pups were lower than the new toxicity reference value of1,300 *μ*g/kg lipid for risk of immunotoxicity and endocrine disruption in harbor seals [67]. Other POPs with a similar mode of toxicity such as polybrominated diphenyl ether (PBDEs) flame retardants, which were also detected recently in these animals [34], can further exacerbate the immune and endocrine response. A compromised immune and endocrine system impairs the ability of animals to combat disease and to successfully reproduce.
